Ultralow dark current in near-infrared perovskite photodiodes by reducing charge injection and interfacial charge generation.

Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in achieving high detectivity in PPDs is lowering the dark current density (J _D ) and noise current (i _n ). This is commonly accomplished using charge-blocking layers to reduce charge injection. By analyzing the temperature dependence of J _D for lead-tin based PPDs with different bandgaps and electron-blocking layers (EBL), we demonstrate that while EBLs eliminate electron injection, they facilitate undesired thermal charge generation at the EBL-perovskite interface. The interfacial energy offset between the EBL and the perovskite determines the magnitude and activation energy of J _D . By increasing this offset we realized a PPD with ultralow J _D and i _n of 5 × 10 ^-8  mA cm ^-2 and 2 × 10 ^-14  A Hz ^-1/2 , respectively, and wavelength sensitivity up to 1050 nm, establishing a new design principle to maximize detectivity in perovskite photodiodes.
(© 2021. The Author(s).)